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Seasonal Cycle and Annual Reversal of the Somali Current in an Eddy-Resolving Global Ocean Model

Author(s):

He Wang - Scripps Institution of Oceanography (SIO)

Julie L. McClean - Scripps Institution of Oceanography (SIO)

Lynne D. Talley - Scripps Institution of Oceanography (SIO)

Stephen Yeager - National Center for Atmospheric Research (NCAR)

Title

Seasonal Cycle and Annual Reversal of the Somali Current in an Eddy-Resolving Global Ocean Model

Publication Type

Journal Article

Year of Publication

2018

Journal

Journal of Geophysical Research: Oceans

Volume

123

Number

9

Pages

6562-6580

Date Published

10/2018

Abstract

The annual cycle of the Somali Current is studied using a forced strongly eddy‐active global ocean general circulation model. The annual cycle and timing of the reversal of the Somali Current differ depending on the location along the coast of northeastern Africa. A momentum budget analysis calculated from the model output shows that both annual Rossby waves and the life cycle of the Great Whirl impact the northern part of the Somali Current (roughly 5°N to 10°N). In particular, the nonlinear term is of leading order importance when the Great Whirl is present. This is in contrast to the leading‐order geostrophic balance between 2°N and 5°N. South of 2°N, equatorial dynamics prevail, and the nonlinear term is again important, and its reversal is strongly affected by the northward-flowing East African Coastal Current. Alongshore wind forcing is influential at all latitudes, but only the transition in flow direction during boreal spring between 2°N and 5°N directly follows that of the wind.

The annual cycle of the Somali Current is studied using a forced strongly eddy‐active global ocean general circulation model. The annual cycle and timing of the reversal of the Somali Current differ depending on the location along the coast of northeastern Africa. A momentum budget analysis calculated from the model output shows that both annual Rossby waves and the life cycle of the Great Whirl impact the northern part of the Somali Current (roughly 5°N to 10°N). In particular, the nonlinear term is of leading order importance when the Great Whirl is present. This is in contrast to the leading‐order geostrophic balance between 2°N and 5°N. South of 2°N, equatorial dynamics prevail, and the nonlinear term is again important, and its reversal is strongly affected by the northward-flowing East African Coastal Current. Alongshore wind forcing is influential at all latitudes, but only the transition in flow direction during boreal spring between 2°N and 5°N directly follows that of the wind.